Recently, as an environment problem, such as global warming, has emerged, regulations on exhaust gas have been enhanced, and particularly, a strict standard is applied to the emission quantity of exhaust gas of an automobile.
Particularly, under the EURO-6, in a case of a diesel engine for a car, the quantity of NOx generated needs to be decreased to a level of 80 mg/km, and in this respect, the automobile related companies have adopted new technologies, such as exhaust gas recirculation (EGR), lean NOx trap (LNT), and selective catalyst reduction (SCR).
An EGR device may include a high pressure EGR (HP-EGR) device, which recirculates exhaust gas at a front end of a catalyst, and a low pressure EGR (LP-EGR) device, which recirculates exhaust gas at a rear end of a diesel particle filter (DPF) and recirculates the recirculated exhaust gas to a front end of a turbo charger.
In order to cool the recirculated exhaust gas, an EGR cooler is disposed in an exhaust gas recirculation line, and the EGR cooler may be made of a stainless material having high corrosion resistivity to a high temperature state and condensate water.
However, the EGR cooler made of the stainless material is heavy, has low heat transmission efficiency, and has a poor molding property, and the entire components are expensive. Accordingly, research on the EGR cooler, which has high heat transmission efficiency, has an excellent molding property, and is made of aluminum, and of which components are relatively cheap, has been conducted.
Typically, aluminum A1100 that is based on pure aluminum (A1xxx) and A3003 that is based on aluminum-manganese (A3xxx) are used in a fin and a tube of a heat exchanger, which is a cooler, and a temperature of recirculated exhaust gas is about 550° C.
Further, corrosive ions, such as Cl—, SO42-, and NO3-, exist as a component of condensate water, so that the aluminum-based fin or tube may be damaged in a high temperature environment and a corrosive environment. In this respect, research on an aluminum sheet having high strength and high corrosion resistivity is conducted.
FIG. 5 is a perspective view of a cross-section of a part of a tube applied to an EGR cooler.
Referring to FIG. 5, an EGR cooler includes a tube 200, inside of which exhaust gas passes through, and outside of which a coolant passes through.
The tube 200 includes two sheets, which are disposed while having a predetermined interval, and an embossing 500 protruding inwardly are formed in the sheets. Further, leading portions of the embossing 500, which face each other, are brazed to each other to configure the tube 200.
The EGR cooler has a structure, in which exhaust gas or a coolant passes through an internal space, in which the embossing 500 is formed, and the coolant or the exhaust gas passes through an external space, and a brazed portion 505 of the embossing 500 is corroded by a high temperature and condensate water, so that a leakage is generated, thereby degrading general durability.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.